Multiple Charge States of Ag Atoms on Ultrathin NaCl Films

Abstract

A combined study using density functional calculations and scanning tunneling microscopy experiments shows that individual silver adatoms on ultrathin sodium chloride films on copper surfaces are stable in three different charge states-neutral, negatively, and positively charged adatoms. The charge states of the individual adatoms were manipulated by voltage pulses. The key parameters determining the stability of various charge states are identified and discussed within a simple model.

Forces from periodic charging of adsorbed molecules

“…STM permits injecting charge carriers very locally in the weak coupling limit, namely, in the tunneling regime. [28][29][30][31][32][33][34][35] Atomic force microscopy (AFM) in combined STM/AFM setups complements STM experiments by providing information of the molecular geometry-independent from the conductance. 36,37 In recent years, this has been applied to gain insight into the geometry changes associated with toggling single-molecule switches.…”

Implementation of simple logic gates on gold–ammonia bonding patterns in different charge states

“…These different electrostatic properties can be used to select one or the other conformer in the logic schemes discussed in Section 3.2 below (see also discussion in Appendix). The alternation Z ⇒ Z' can be achieved either by using different metallic supporters or/and applied voltage, [39][40][41][42] by the optical 'negative ion -to neutral -to positive ion', NeNePo experimental setup [43][44][45][46], or by resonant photoionization. [47] For Z = 0, conformer I has one anchoring Au-N 1 bond and one conventional intermolecular Table 1, that allow to uniquely characterize each conformer.…”

Manipulation of the Charge State of Single Au Atoms on Insulating Multilayer Films

“…Perhaps the most severe difficulty is that scanning tunneling microscopy (STM) is ruled out by the insulating nature of the samples. So far, charge-state manipulation has been shown only for single atoms and molecules on bi-and trilayer NaCl films [3][4][5][6][7], on which STM operation is enabled by a still high tunneling probability through the film and charge states are stabilized by large ionic relaxations of the NaCl film. In contrast to charge stabilization on bulk insulators, the charge-state-stabilization mechanism on films with nonvanishing tunneling probability depends strongly on the specific properties of adsorbate, film, and substrate [4], and only selected charge states can be stabilized.…”

“…So far, charge-state manipulation has been shown only for single atoms and molecules on bi-and trilayer NaCl films [3][4][5][6][7], on which STM operation is enabled by a still high tunneling probability through the film and charge states are stabilized by large ionic relaxations of the NaCl film. In contrast to charge stabilization on bulk insulators, the charge-state-stabilization mechanism on films with nonvanishing tunneling probability depends strongly on the specific properties of adsorbate, film, and substrate [4], and only selected charge states can be stabilized. Despite its important implications for catalysis as well, the transition from films with nonvanishing tunneling probability to bulklike insulating films [8][9][10] in the context of chargestate manipulation is poorly understood.…”

“…[4], the key parameters determining the stability of various charge states are discussed within a simple model. Based on this model, we ascribe the spontaneous decay of the Au 0 and Au þ charge states on NaCl films grown on Cu(311) to the significantly reduced work function of Cu(311) (4.31 eV [27], as compared to 4.59 eV for Cu(100) and 4.94 eV for Cu(111) [28]), which shifts the affinity level of Au 0 for an unrelaxed ion lattice closer to the Fermi level of the Cu(311) substrate (≈0.8 eV above E F [29]).…”